Defining: "Douchebags"

People always throw out the term Douchebag as in, "Man that bar had so many douchebags in it."  I think we all have a general sense about this class of character, but how about some specifics?  In this post I try to define the term Douchebag, who are they, what are their habits, and how can they be identified.  This is a three-part series.